Methanesulfonic acid (H3CSO3H, MSA) is a strong organic acid which is used for a multiplicity of different processes, for example for electroplating processes, in chemical synthesis, in cleaning agents or for tertiary mineral oil production.
MSA can be prepared by various processes, for example by oxidation of methanethiol by means of Cl2, followed by hydrolysis, as disclosed, for example, in U.S. Pat. No. 3,626,004. Alternatively, it is also possible to oxidize dimethyl disulfide with Cl2. The processes lead to MSA which, in spite of purification, still comprises significant amounts of chlorine compounds, for example chloride.
WO 00/31027 discloses a process for oxidizing dimethyl disulfide with nitric acid to MSA, the oxides of nitrogen which are formed being reacted with O2 to give nitric acid again and this being recycled to the process. CN1 810 780 A discloses a process in which ammonium sulfite and/or ammonium hydrogen sulfite is reacted with dimethyl sulfate to give ammonium methanesulfonate and ammonium sulfate. The ammonium sulfate can be precipitated with Ca2+ as CaSO4. MSA can be liberated from the remaining Ca(CH3SO3)2 with sulfuric acid and can be worked up, once again CaSO4 being precipitated. EP 906 904 A2 discloses a process in which sodium sulfite is reacted with dimethyl sulfate. MSA can be liberated from the resulting mixture after acidification with concentrated sulfuric acid. The three last mentioned processes have the advantage that the MSA obtained is virtually free of chlorine compounds.
As an acid, MSA can of course attack metals. Low-alloy steels are usually not stable to MSA. WO 2006/092439 A1 investigates the corrosion behavior of low-alloy steel for pressure containers (material number 1.0425, about 0.3% of Cr, about 0.3% of Ni, from 0.8 to 1.4% of Mn) in 70% strength MSA. The steel is attacked by MSA to a substantially lesser extent than by hydrochloric acid but the addition of corrosion inhibitors is necessary in order to reduce the removal of metal to an acceptable level.
In relevant brochures, polyethylene, polypropylene, polyester, polystyrene, glass enamel, ceramics, tantalum or zirconium are proposed as materials for handling methanesulfonic acid. Furthermore, the use of steel having a material number 1.4539 and 1.4591 was also proposed (Lutropur® MSA brochure, “Die “grüne” Säure für Reiniger”, 10/2005 edition, BASF SE, Ludwigshafen). Such steels are high-alloy chromium nickel steel (1.4539 about 20% of Cr, about 25% of Ni, 1.4591 about 33% of Cr, about 31% of Ni).
As a material for apparatuses for handling MSA, for example for storage and/or transport, the use of steel having sufficient resistance to MSA is highly desirable because only in this way is it possible to avoid providing containers, apparatuses and pipelines with internal linings comprising corrosion-resistant materials. The abovementioned steels are very expensive special steels which are difficult to procure. Workpieces comprising these steels are accordingly expensive and the use of such steels for relatively large components, such as, for example, tanks, is therefore uneconomical.